I have an Htc Desire and I'm using the headset that came with it. During a call yesterday the other party stopped hearing me. I unplugged the headset and continued with the conversation normally. Today I checked the headphones again before buying a new pair and indeed the other person couldn't hear me. What was really surprising is that I could hear myself, echo with about a second of delay. So, electronically my headphones work. Is there something broken in my phone?

Update: I just tried the Skype test call and it worked just fine, so it seems to be my headset when making phone calls, which is really weird.